FRANKENHONDA II the 1982 DOHC CB 750F2 Build

cb250nproject

If you can make it better do so
Well things I over looked, the clutch I thought it was fine but it started slipping on the dyno ... I have a feeling this is going to turn out to be an expensive venture... can’t put a price on happiness.

Rex picked up that the foot pegs will need a full rework... this may take a few weekends in OMM shed to perfect


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cb250nproject

If you can make it better do so
I don’t have any dyno paperwork as the bikes still in the shop but Rex said she’s making 78hp at 9500 rpm, I think that’s about 11hp over stock.

If I can get I back tomorrow the next challenge is getting these rear sets sorted, hopefully then I can spend some time getting to know Frankenhonda


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cb250nproject

If you can make it better do so
11HP over stock is pretty good.
It’s been bored out to 823cc, I wasn’t really sure what to expect as I couldn’t really find any solid figures for a set up like mine. I have a friend who bored his DOHC out to 836 who got 87 hp.

I’d love to find some scales that could weigh the bike to see how much weight I’ve dropped from stock by losing all the fairing etc.

At the end of the day as long as it reliable, sounds fast, and can do the ton I’ll be one happy camper.


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cb250nproject

If you can make it better do so
There's many a slip between dress and drawers mate but looks like you've got it licked. Nicely done.

For the bolts, I didn't use loctite on the case bolts, but did apply some molybdenum disulphide high pressure grease to the bolt threads. For your snazzy new stainless cover bolts, they'll come with simple instructions - use a little loctite or copper anti-seize on the bolt threads and you're golden and don't torque them to the same spec you would the OEM cover bolts, but a little less.

By the way, your head bolts can be torqued higher than stated in the manual. Manual states 29ft lbs (I think) but - as yours is the F model - you can torque those bad boys down to 35ft lbs. Your studs look like this, right? -



(If so yeah, you can torque those head bolts down to 35ft lbs).
Hey Jimbonaut where did you find the 35 ft lbs torque setting for the head bolts ? I've just noticed a little oil seeping out of the gasket, I know I did all of mine down to 29ft, wondering if that's not enough
 

cb250nproject

If you can make it better do so
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so this is the dyno from Rex.

Rex modified the shifter to come straight off the shaft. It was only meant to be a temporary so he could dyno it but I’m starting to get use to it. So it’s GP shifting from here on in

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So I rode home few things that stood out was, the location of my indicator switches was too far around the bar and needs to be rotated back towards me for easier access and that the brake and clutch levers needed to be adjusted also
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also I had to re set the m unit so that the indicators would turn off after 10 sec

Unfortunately I also noticed oil coming from the cylinder head gasket, on the front left side of the motor. I took the cam cover off and re-torqued the cylinder head bolts.

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The weather is miserable at the moment, so I will wait until tomorrow morning, to give her a wash and hopefully take her for another test ride, with less leaking this time.



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cb250nproject

If you can make it better do so
Well with a little help from a good friend the kick stand has now been shortened
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Hopefully I can pick it up later today.

Also on the to do list I got from Rex; support carburettor rack, put ring connectors rather than spade connectors to ignition coils, strap down ignition unit, lower the rear sets— plus I need to fabricate a chain guard.

I’m also looking at the rear swing arm thinking I need some kind of small mud guard on it to stop some of the mud being flicked up from the road— not sure what to make this out of surely not another fiber glassing saga


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cb250nproject

If you can make it better do so
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The Jimbonaut

Active Member
Hey Jimbonaut where did you find the 35 ft lbs torque setting for the head bolts ? I've just noticed a little oil seeping out of the gasket, I know I did all of mine down to 29ft, wondering if that's not enough
I'm a member of another forum - cb1100f.net (it's an absolute goldmine) - and one of the members there told me. The cylinder studs on the DOHC F models are different from the other 750's, allowing them to be torqued to a higher spec. 35ft lbs, no problem.
 

teazer

Active Member
DTT BOTM WINNER
What does the FSM say about the head bolt torque setting? 35 foot pounds sounds like a lot to seal a head.
 

The Jimbonaut

Active Member
It's all good - you're good to 35ft lbs on those studs but I'd probably do the same as you if Rex had told me differently. From the horse's mouth and all that. Hope you get that leak squared away either way.
 

The Jimbonaut

Active Member
Incidentally - the FSM does indeed state that the max torque for the studs is 29ft lbs, but not for these F model studs. They're machined differently (they have a spiral thread running up them) whereas the studs in the FSM are the standard K and C model studs (which can only be torqued to 29ft lbs).
 

cb250nproject

If you can make it better do so
I haven't had a chance to take her for another bust to see if the issues been resolved, I'm still waiting to pick up my kick stand, no point getting stranded somewhere and not being able to put her on the side stand while I calmly resolve the issue without cursing :D
 

cb250nproject

If you can make it better do so
Cheers Pete,

I managed to get the Dyna box secured (liquid nails and Velcro) resprayed the plate bracket black so it blends in more, and the front mud guard, as it had a tiny scratch in it that caught my eye every time I approached the bike. Also I got all the coil terminals changed over from spade to ring.

All small things but all the 1%ers add up

Next two big missions are chain guard, foot pegs.... then test ride again and pray the leak from the gasket seal has been fixed.

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cb250nproject

If you can make it better do so
Engine bolts arrived today.

The exhaust will need to be removed to access all the lower case bolts. There are two bolt on either side of the oil filter that require me to remove the oil filter... I think I will be waiting until my next service to do that as this is like the 3rd lot of oil through the bike in as many weeks.

Still haven’t managed to calibrate the speedo as the wifey is feeling ill and it’s a hard sell to get her leave the comfort of the house to help out


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